As illustrated in FIG. 1, a power supply device for an environmentally-friendly vehicle, such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle, includes a high voltage battery 10, and an inverter 12 for converting a direct-current voltage of the high voltage battery 10 into an alternating current voltage to supply the converted voltage to a motor 11 for driving. A 12 V auxiliary battery 14 supplies a direct current voltage to an electric component of the vehicle when the vehicle starts to drive and supplies a voltage necessary for operating a main relay of the high voltage battery. A DC-DC converter 13 converts the direct current voltage received from the high voltage battery to charge the auxiliary battery 14 or to supply the converted voltage to a 12 V electric load 15, and the like.
The DC-DC converter 13 converts a voltage of the high voltage battery into a low voltage (+12 V) to charge the auxiliary battery, such as an alternator of an internal combustion engine, and to supply the converted voltage to various types of electric components (electric loads).
In this case, a connection line between the high voltage battery 10 and the DC-DC converter 13, and a line connected from the DC-DC converter 13 to the auxiliary battery 14 and the electric load 15 is formed of a cable.
The power supply device for the environmentally-friendly vehicle has the following problem.
Impedance of the output terminal of the DC-DC converter may be increased by an abnormal state (damage by external force, and the like) of the cable connecting the respective elements of the power supply device or corrosion of the cable due to aging of the respective elements of the power supply device.
When the impedance of the output terminal of the DC-DC converter is increased, a voltage is dropped in an input terminal of the auxiliary battery or an electronic load receiving the voltage from the DC-DC converter, and the voltage drop decreases a charging current for the auxiliary battery, and directly causes the discharge of the auxiliary battery.
In the state where the charging current of the auxiliary battery is decreased so that the voltage is dropped to a normal level or lower, the auxiliary battery fails to supply a voltage appropriate to an operation voltage of each controller, so that starting of the hybrid vehicle may be impossible.
A fault diagnosis for the impedance increase is not performed, so that an erroneous repair (replacement of only the auxiliary battery) may be caused, and as a result, the auxiliary battery is discharged again.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.